FIG. 1 is an overall architecture diagram of a Long Term Evolution (LTE) system in the related art, as shown in FIG. 1, and the architecture comprises a Mobility Management Entity (MME) and a Serving GetWay (SGW). A UU interface is between User Equipment (UE) (or called a terminal) and a eNodeB (eNB), an S1-MME interface is between the eNB and the MME, an S1-U interface is between the eNB and the SGW, and an X2 interface is between the eNBs. FIG. 2 is a schematic diagram of a protocol architecture of a control plane and a user plane among the UE and the eNB and a core network (MME and SGW), at the left side of FIG. 2, interfaces between the UE and the eNB in the LTE are divided into the following several protocol layers from bottom to top: a Physical (PHY) layer, a Media Access Control (MAC) layer, a Radio Link Control (RLC) layer, a Packet Data Convergence Protocol (PDCP) layer and a Radio Resource Control (RRC) layer. At the right side of FIG. 2, the user plane protocol stack of the interface between the UE and the eNB in the LTE are divided into the following several protocol layers from bottom to top: the PHY, the MAC, the RLC and the PDCP. The PHY layer transmits information to the MAC or a higher layer mainly by a transmission channel; the MAC layer provides data transmission and is responsible for radio resource allocation mainly by a logical channel, so as to complete functions such as Hybrid Automatic Repeat Request (HARQ), Scheduling (SCH) and priority processing and Multiplexing (MUX) and De-multiplexing; the RLC layer mainly provides services for sectioning and retransmitting user plane data and control plane data; the PDCP layer is mainly provided for transmitting the user plane data to the RRC layer or an upper layer of the user plane, and the RRC layer mainly completes at least one of the following operations: Broadcast, Paging, wireless resource control connection management, radio bearer control, mobile function and terminal measurement reporting and control.
In order to provide a higher rate data for a mobile subscriber, a Carrier Aggregation (CA) technique is proposed in the Long Term Evolution Advance (LTE-A) system, of which the purpose is to provide a larger broadband for UE with a corresponding capacity so as to improve the peak rate of the UE. In the LTE, the maximum downlink transmission bandwidth supported by the system is 20 MHz, after entering a connected state, the UE may communicate with a network side through a cell. The carrier aggregation technique is a technique in which two or more Component Carriers (CC) are aggregated to support a transmission bandwidth which is larger than 20 MHz and is not larger than 100 MHz. Through the carrier aggregation technique, the UE with a corresponding capacity may receive and send dada on a plurality of cells under the same base station at the same time. The differences of the interface protocol stack between the UE and the base station is mainly reflected on the MAC layer and PHY layer. The PHY layer is specialized for the CC, which is different from the MAC layer, in the MAC layer, the HARQ is specialized for the CC, and the scheduling, the priority processing and multiplexing and de-multiplexing are public for the CC.
Due to lack of spectrum resources and the sharp increase of mass flow service of mobile subscribers, the requirement of using a high frequency point, such as 3.5 GHz, for hot-point covering is increasingly obvious. A node with low power becomes a new application scenario, so as to increase the user throughput and enhance the mobile performance. However, because a signal with a high frequency point attenuates strongly, the coverage area of a new cell is relatively small, moreover, the new cell does not share the same station with the existing cell, when a user moves among these new cells or moves between the new cell and the existing cell, it will certainly lead to a frequent switching process, so that user information is frequently transferred among base stations, thus leading to a great signalling impact to the core network.